To investigate potential mechanisms of immunotoxicity of ATR in mice, in particular the roles of oxidative stress and alterations in intracellular calcium homeostasis in the process, ROS production, DNA damage, intracellular Ca2+ concentration in splenocytes, as well as AOPP levels and GSH/GSSG ratios in serum, and expression of some key gene and proteins related to oxidative stress in the spleen were measured. This evidence concerns the gene ATR and immune system toxicity.